1. Field of the Invention
The present invention is directed to an electric-supply-switch relay-circuit, and more particularly, to an electric-supply-switch relay-circuit in which the switching operation of a relay is stabilized by means of an electronic circuit and which can be used in an undersea branch apparatus or the like.
2. Description of the Prior Art
In a submarine-cable communication system, using optical-repeater stations or the like, to supply current to said repeater stations, an under-water branch apparatus is used which branches submarine cables to a plurality of cable stations (landing stations). When there is a defect in any one of the submarine cables, said undersea branch apparatus removes the defective cable from the electric supply route in order to establish an alternative electricity supply route among the remaining cables, by using electric-supply-switch relays.
The electric-supply-switch relays used in the undersea branch apparatus each need to function as electric-supply-switch sequencers which operate under the control of the cable houses. Hence, in a more complex system in which systems are connected to each other in series, even more precise current control is necessary. Otherwise, in the worst case, a malfunction of the electric-supply sequence the will cause problems in the electric-supply routes.
However, the operating current for operating the relays varies within a certain range, and therefore, to avoid the influence of the variation in the relay operating current, certain approaches must be taken, such as the selection of the operating characteristics of the relays. However, when such an approach is taken, the relays become expensive. Further, provision of the relay operating current adjusting resistor to adjust a number of relays independently according to a predetermined connection sequence is not desirable in terms of the number of process steps, the reliability and the like.